Effect of ethyl methanesulfonate on the fertility of barley

Abstract

The effect of ethyl methanesulfonate (EMS) on the fertility of barley was cytologically and genetically studied. The fertility of the M 1 generation of seeds treated with 3% EMS at 24°C for 3 hr was reduced to 20·8 per cent seed setting. In the cytological study of root-tips from seeds treated with 2, 3 and 4% EMS, the percentage of abnormal anaphases at the first mitotic cycle was 30·1, 45·5 and 61·7 per cent, respectively, whereas 30,000 R of X-rays resulted in 23·0 per cent. The relative ratio of bridges to fragments produced by EMS was considerably lower than that of X-rays. An effect of EMS on cell division which was similar to that of colchicine was found after seed treatment with 3 and 4% EMS. The percentage of M 1 spikes with chromosomal re-arrangements after seed treatment with 3% EMS was only 3 per cent, which coincided with the frequency of double bridges in the root-tip study. Other anomalies in M 1 meiosis were also observed, such as dissynchronization of the stages of PMCs, actively dividing tapetal cells during pachytene or even metaphase, extreme stickiness of chromosomes, tetrad cells without nucleus and abnormal form of tetrads. Genetic studies were carried out up to M 4 generation in order to gain insight into the pattern of inheritance of sterility. The studies reveal that the sterility induced is heritable. The modes of segregation suggest that the heritable change occurs in the nucleus rather than in the cytoplasm. The studies also suggest that, in contrast to the effects of X-rays, a large part of sterility has a diplontic and not a haplontic nature. It is assumed that small “invisible” deficiencies are the main cause of sterility.